Receiver conditioning in voice communication, particularly telephone communication, primarily addresses the problems of weak incoming electrical voice signals and large amplitude electrical signals which produce acoustic shock to the listener's eardrum. To alleviate the problem of weak incoming electrical voice signals, additional receiver gain is beneficial. To obviate acoustic shock from incoming electrical signals of excessive amplitude, compression of the incoming signal is provided to linearly reduce the amplitude and at the same time avoid introducing harmonic distortion.
Heretofore, so-called "hard-of-hearing" amplifier devices have been utilized as a solution to weak incoming voice signals and high background noise environment problems. Illustrative of these devices is the Western Electric Co. 153B amplifier. However, such devices do not provide for compression of large amplitude incoming signals, with the result being that the listener is left vulnerable to very high sound pressure levels at the ear termed "acoustic shock".
A device heretofore utilized to provide signal gain yet compress received audio signals to a specific maximum level without harmonic distortion is the Model ROC 300 manufactured by Plantronics, Inc., Santa Cruz, Calif. 95060. The ROC device is a discrete components circuit type device, and thus it is rather large physically. Also the ROC device is powered by an external power supply of 24 or 48 volts. The necessity of an external power supply limits the ROC device to installation in a console, for example, in PABX systems.